Gravel packing is a term known in the oil and gas business which involves, in one class of applications, the placement of a granular material outside of casing perforations to improve the performance of the well by causing the formation material to be constrained, thus allowing formation fluids better access to the tubing string and ultimately to the surface. In the past this has been accomplished by placing a screen in the appropriate location and pumping down, in slurry form, the fluid bearing the granular material so that it could deposit. Problems have ensued with this type of procedure because with the material being pumped from above the top of the perforated interval, a potential existed for bridges and blocks to form uphole which would in turn prevent adequate and thorough high-density packing and distribution of the granular material out, across and around the entire perforated interval and length of the screen. Incomplete packing of the casing-screen annulus, perforations, and areas outside of the perforated casing are well-known causes of sand control failure and/or poor gravel-packed well productivity. Such incomplete packing is the result of efforts to pack a lengthy interval where significant differences in perforation injectivity prevent packing of all perforations.
The apparatus and method of the present invention address this potential faulty distribution and packing problem by providing a technique to pack within and outside of the perforated interval and outside of the screen systematically in smaller segments from the bottom up. With the technique of the present invention, the risk of bridging or blocking at the upper end, precluding adequate distribution at the lower end, is greatly reduced if not eliminated. Additionally, by packing smaller segments systematically, the problem of incomplete perforation packing is reduced if not eliminated. Thus, a more efficient and effective gravel-pack job can be accomplished with the apparatus.
Accordingly, it is an object of the present invention to facilitate thorough distribution of the granular material around a screen and within and outside of the perforated interval by virtue of deposition of the granular material around the screen and perforated interval from the bottom up. It is also an object of the present invention to improve performance of wells by providing a more efficient and productive gravel pack for the well operator.